JPS59129755A - Stainless steel cast with high corrosion fatigue strength - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This invention relates to martensitic stainless steel cast steel.

River water turbine runners in harsh corrosive environments, chemical plants,
Stainless steel cast steel with both excellent FFt corrosion resistance and corrosion fatigue strength is required for food industry machinery, paper manufacturing machinery, desalination equipment, etc.

Conventionally, for example, water turbine runner materials mainly contained 73% Cr.
-Ni-based mar*nsitic stainless steel cast steel has been used, but although this type of stainless steel cast steel has excellent strength, toughness, and cavitation resistance, it has low chromium content and therefore has poor corrosion resistance compared to austenitic stainless steel. I couldn't say it was enough.

In other words, materials with high corrosion fatigue strength are an absolute requirement for water turbine runners, desalination equipment, marine structures, etc. that are used in severe corrosive environments, but the materials that have been used in the past are Since 73%-Nl based cast steel has insufficient corrosion resistance and corrosion fatigue strength, there has been a demand for the development of stainless steel cast steel that has both superior corrosion resistance and corrosion fatigue strength.

The present invention was made in view of the above, and it is an object of the present invention to provide a martensitic stainless steel cast steel which has the excellent mechanical properties of martensitic stainless steel cast steels and has greatly improved corrosion resistance, particularly corrosion fatigue strength. purpose.

The purpose is to reduce Cθ10 inches or less on a weight basis + Si/θ
0chi or less + Mn ojθ-709% + Ni'1
．． θ0=600%, Cr/6θ0-7g00%, M
o 03'0-/jθ This is achieved using martensitic stainless steel cast steel containing Fe and the remainder consisting of Fe and unavoidable impurities.

The present invention will be explained in more detail.

As mentioned above, the martensitic stainless steel fFJI4 of the present invention has alloy components of c0/θ or less, Si/: θθ% or less, MnO, 3θ-Zθ0 ratio on a weight basis.

Ni MIG 0-Otsu 00%, CR/Otsu 00-/g, 00%,
M.

The reason why the content of the component elements is limited in this way will be explained.

Although C has the effect of improving the strength of martensite, excessive addition of C significantly reduces toughness and corrosion resistance, so the upper limit was set at 87%.

Si and Mn are in the composition range of ordinary martensitic stainless steel in the steel of the present invention, that is, Si iθ
Below the θ coefficient, Mno3θ−, 100%, and within this range, the steel of the present invention can be easily manufactured industrially by atmospheric melting.

Ni is an element that is extremely effective in improving corrosion resistance as well as strength and toughness due to its combined effect with Cr.The beam θ0-6 is used to convert stainless steel into martensitic material.
Section 00 is appropriate.

Cru stainless steel is an important element that has the effect of improving corrosion resistance, but in order to significantly improve corrosion resistance, it must be contained at 73.00% or more. The range is limited to /O 0θ-/ and θθ because the increase in θ and impairs toughness.

Mo is an element that significantly improves local corrosion resistance, but
The effect is insufficient below the θS0 coefficient; on the other hand, /! ;
If it exceeds 0%, the addition effect will be saturated and the ferrite phase will increase, leading to a decrease in toughness, so the range was limited to θSθ-/80%.

In addition, although the reason for limiting the above-mentioned component ranges has been explained with respect to the effects of each component element, the effects of the present invention include, in addition to the above,
This is brought about by the interaction or synergistic action of these components.

Next, the features of the present invention will be explained in detail based on actual examples and in comparison with comparative examples.

Table 1 shows the chemical compositions of comparative steels (types) and an example of the steel of the present invention.

Table 1 Chemical composition of test steel (wt%) Next, Table 2 shows the mechanical properties of each steel type shown in Table 1, Figure 1 shows the results of anode polarization measurement in salt water, and the corrosion fatigue test results (S- N curves) are shown in FIG.

Table 2 Mechanical Properties of Test Steel The mechanical properties shown in Table 2 show that the strength level is /3Gr-3, which is equal to or higher than Ni cast steel, and is much higher than other comparative steels. On the other hand, the notch toughness is comparable to /3Gr-finished Ni cast steel.

Regarding corrosion resistance, the anode polarization curve shown in Figure 1 shows that the anode peak current and passivation holding current decrease as the amount of Gr increases. Gr-g NiMo r/6.j Gr
-'1. ．． ! ; Ni) It is clear that the eating habits of llif are extremely superior to those of Ni). From this, / 3 Gr 3 c! which is similar to the above comparison steel type! It is clear that the steel of the present invention has extremely superior corrosion resistance compared to 7'Ni cast steel.

Furthermore, looking at the corrosion fatigue strength (S-N curve) shown in Figure 2, the steel of the present invention is different from other comparative steel types (/To and Mo).
v/3Cr/Ni/Mo+/JGr
-GNi, /J' -f) It is clear that the fatigue life is extremely superior to that of the steels shown in Table 1, which are similar to these comparative steels. .

As explained above, it is clear that the steel of the present invention has excellent mechanical properties and is extremely excellent in corrosion resistance and corrosion fatigue strength, and is suitable for use in a severe corrosive environment.

Procedural amendment document February 25, 1980 Director General of the Patent Office 1. Indication of case 1988 Patent Application No. 5254 2. Title of invention Stainless steel cast copper having high corrosion fatigue strength 3. Related: Patent applicant Co., Ltd. Japan Steel Works 4, Agent address: 5-9-20, 1-9, Akasaka, Minato-ku, Tokyo, No date of amendment order, (voluntary amendment) 6, Details of the invention in the specification subject to amendment Details of the Z correction in the explanation column (]) Page 2, line 10 of the specification [16%-Nil [
Corrected with 16% 0r-Nil.

(2) Table 2 on page 6 of the specification is amended as shown in the attached sheet.

(3) 2nd line r13Gr under Table 2 on page 6 of the specification
Correct J to [13 crJ.

(4) ``Grj'' in line 4 of Table 2 on page 6 of the specification is corrected to ``CrJ.''

(5) Page 6 of the specification, line 7 under Table 2 rG rJ
is corrected as ``CrJ.

(6) r13Gr, line 8 under Table 2, page 6 of the specification
Correct J to 130rJ.

(7) Line 9 r165G under Table 2 on page 6 of the specification
Correct rJ to 1-1650rJ.

(8) Page 6, line 2 of the specification [Replacing 13Grj with “16C
Correct it as "r".

(9) Specification letter page 7 line 7 r13Gr-4J [1
Corrected to 3cr-4J.

Table 2 Mechanical properties of test steel Procedure supplement (method) % formula % 1. Indication of incident 1982 Patent Application No. 5254 2
, Title of the invention: Stainless steel cast steel with high corrosion fatigue strength 3, Relationship to the amended case Patent applicant (421) Japan Steel Works, Ltd. 4, Agent address: 1-9-20 Akasaka, Minato-ku, Tokyo 5. Date of amendment order: Date of dispatch: April 28, 1982

Claims (1)

[Claims] Based on the amount of X, Cθ/θ or less + Si/: θθ or less. MnO3; 0-100% + Ni4t, θθ-Otsu θθ%,
Cr/6.00-7g, 00%, Mo 0.30-1
．． A martensitic stainless steel cast steel having high corrosion fatigue strength, characterized by containing 50% Fe and the remainder consisting of Fe and unavoidable impurities.